Neodymium magnets are a molding sintered product including neodymium (Nd), iron oxide (Fe), and boron (B) as main components, and exhibit excellent magnetic characteristics. One of the methods for securing high coercive force of a neodymium magnetic powder is a method for using the neodymium magnetic powder by adding a heavy rare earth such as Dy to increase coercive force at room temperature. However, it seems that there is a limitation in recently using a heavy rare earth metal such as Dy as a material in the future due to the scarcity of the heavy rare earth metal and a soaring increase in prices resulting therefrom.
As described above, the imbalance problems between demand and supply of rare earth element resources have become a big obstacle to the supply of high-performance motors required for the next-generation industry, and therefore, there is a need for developing a novel high-performance magnetic material capable of replacing rare earth magnets.
Meanwhile, MnBi in the low-temperature phase (LTP) exhibiting ferromagnetic characteristics is a rare earth-free material permanent magnet, and is characterized to have a larger coercive force than an Nd2Fe14B permanent magnet at a temperature of 150° C. or more because the coercive force has a positive temperature coefficient at a temperature interval of −123 to 277° C.
Therefore, an MnBi-based magnet is a material suitable for being applied to motors which are driven at high temperature (100 to 200° C.). When compared to other magnets in terms of the (BH)max value which exhibits a magnetic performance index, the MnBi-based magnet is better than the existing ferrite permanent magnet in terms of performance and may implement a performance which is equal to or more than that of rare earth Nd2Fe14B bond magnets, and thus is a material capable of replacing these magnets.
Throughout the present specification, a plurality of documents are referenced, and citations thereof are indicated. The disclosure of each of the cited documents is incorporated herein by reference in its entirety to describe the level of the technical field to which the present invention pertains and the content of the present invention more apparently.